1. Field of the Invention
This invention relates to mechanical seals, which are fitted to rotating equipment in virtually all types of industries.
A mechanical seal comprises a “floating” component which is mounted axially movably around the rotary shaft of, for example, a pump and a “static” component which is axially fixed, typically being secured to a housing. The floating component has a flat annular end face, i.e. its seal face, directed towards a complementary seal face of the static component. The floating component is urged towards the static component to close the seal faces together to form a sliding face seal, usually by means of one or more spring members. In use, one of the floating and static components rotates; this component is therefore referred to as the rotary component. The other of the floating and static components does not rotate and is referred to as the stationary component.
Those seals whose floating component is rotary are described as rotary seals. If the floating component is stationary, the seal is referred to as a stationary seal.
If the sliding seal between the rotary and stationary components are assembled and pre-set prior to dispatch from the mechanical seal manufacturing premises, the industry terminology for this is “cartridge seal.” Alternatively, if the rotary and stationary components are individually dispatched (unassembled) from the mechanical seal manufacturing premises, the industry terminology for this is “component seal.”
Mechanical seals are used in all types of industries to seal a variety of different process media and operating conditions. The general industry term which defines the area adjacent to the process media is “inboard”. The industry term which defines the area adjacent to the atmospheric side is “outboard.”
Like most industries, the mechanical seal industry is highly competitive. As a result, mechanical seal manufacturers constantly seek methods of improving competitive advantage.
2. Description of the Prior Art
Pressed and formed components are one way in which mechanical seal manufacturers can reduce the manufacturing cost of said component. Unfortunately pressed components can comprise the technical aspects of a single component or said aspects of a combination of components working relative to each other. One such example of this is the drive mechanism between two components working relative to each other.
As pressed components are manufactured from a given thickness of material, the cross-sectional area of the drive mechanism is traditionally thereby limited to a multiplication of said thickness.
Pressed components are generally manufactured from sheet material, typically steel or stainless steel with a material thickness of 0.2 mm to 2.5 mm. Typically, however, most mechanical seal components are pressed using 0.8 mm- to 1.2 mm-thick material.
Pressed components offer the advantage that, in most cases, subsequent machining operations are not necessary. This therefore reduces the manufacturing cost considerably. The disadvantage of using said pressed parts is the effective drive mechanism between said parts.
Gilbert, U.S. Pat. No. 5,725,219 teaches a mechanical seal design whereby two pressed and substantially thin components engage each other via intermeshing castellantions. Said castellations comprised of an open longitudinal end in each member and, when engaged with each other, are intended to transmit the rotational drive between two longitudinal spaced sealing points within the seal assembly.
In practice this design suffers from several drawbacks, namely;                The torsional forces acting on the interface surface between the two substantially thin members which are mounted in a radially resilient member and subjected to equipment vibration, is the equivalent to a person pressing two knife edges together while on a rowing boat in the sea in the middle of a storm. In practice, said thin members radially misalign and rotationally twist inside of each other, thereby negating any substantial rotational drive benefit between the two members.        The longitudinally open ended castellations have sharp edges/corners, given the substantially thin material and their perpendicular position to the longitudinal end of each member. Said sharp edges/corners not only damage the substantially resilient/rubber like sealing member but often damage/cut operators hands during installation of the seal onto the equipment.        In the seals longitudinally uncompressed state, the open ended longitudinal castellations of each member can disengage creating an installation issue. Furthermore, the spring member, positioned between the two longitudinally floating members provides a longitudinal force which is applied directly to the flexible longitudinal sealing element, leading to stretching and/or tearing of said member.        
A design, which offers a mechanical seal component which is fully, or partly, manufactured in an economical manner, such as, e.g., a pressing operation, and which includes a drive design, which is not limited to the material thickness, is deemed to be particularly advantageous.
United Kingdom Patent Application No. 2,391,275 defines a method of improving the drive mechanism in assemblies containing thin, pressed materials. However, because of the substantially annular surface of each member contained in said drive mechanism and the assembly of said members, the invention mechanism is limited to comprise of two separate and substantially different drive member designs; one substantially U-shaped and one substantially L-shaped. Said different drive member designs can lead to assembly errors and/or lead to extended assembly time. Furthermore, the L-shape members are not optimised to provide an improved drive surface area, over and above the thickness of the substantially thin material of construction.
It is therefore deemed to be advantageous if the drive mechanism between two members of a seal incorporates a substantially thick surface drive area, and can be assembled in such a manner that assembly errors are eliminated, assembly time/cost is reduced and subsequent retainment operations to longitudinally constrain said members are eliminated.
Subsequent retainment operations are defined as punching or staking operations which deform at least one component after the assembly of said components thereby prevent at least two parts from disassembling.